Conventional methanol and other gas to liquid (GTL) production systems use natural gas or other hydrocarbon gasses as input fuels and produce liquids, such as, for example, methanol, gasoline or diesel fuel. The feedstock is first converted to syngas (a combination of hydrogen and carbon monoxide, referred to as “hydrogen-rich gas”) in a fuel reformer. These reformers are catalytic reactors which may use, for example, steam reforming, dry reforming (using CO2), partial oxidation or autothermal operation. These techniques include both exothermic conversion reactions, such as partial oxidation, or endothermic ones, such as steam reforming or dry reforming. These systems are typically of substantial size in order to minimize cost, due to substantial economies-of-scale.
Commercial manufacturing plants tend towards the size of “megaplants,” producing, in the case of methanol more than 1 million tons of methanol per year, or in the case of diesel, up to 100,000 barrels/day. There are issues with these very large plants, including long construction periods, with substantial cost overruns (particularly for plants that produce diesel fuel) and construction delays, and difficulty in predicting markets over the long construction period. In addition, to create this amount of methanol, the plant must be supplied with a considerable amount of reactant. Thus, the commercial plants are typically supplied by a pipeline which deliver the necessary reactant gas, or next to natural gas wells of substantial productivity.
For natural gas or biomass based feedstock that are difficult or expensive to transport, conventional commercial manufacturing plants cannot be used. Therefore, it may be desirable to make smaller, lower cost reformers in order to minimize the transportation distance from the collection site. Gaseous streams include natural gas (from shale or other sources) that may be difficult or impossible to introduce into a pipeline. Other examples include small scale isolated gas production, natural gas generated in off-shore drilling rigs and biogas, produced from landfills or from anaerobic digesters.
Therefore, there is a need for lower cost, smaller scale reformer systems to be used in the distributed conversion of gas to methanol and other gas to liquid (GTL) products. This need is particularly strong to fully exploit the increased availability of low cost natural gas.
Furthermore, in order to minimize the cost of the reformer and the complete GTL plant, it would be desirable to integrate the components, including compressors, generators and motors, reformer, gas clean up units, and catalytic reactor for making the fuels such as methanol or Fischer-Tropsch diesel.
In some embodiments, such as partial oxidation and other type of reformers, it would also be attractive to recover a fraction of the energy produced in the process. This energy can be used to make the unit self-reliant in energy, reduce the cost of other subsystems in the GTL plant or converted into electricity for external sale. In addition to the production of fuels, the same system can be employed to produce other chemicals, such as ammonia, in a similar manner.